Thermionic tube



Dec. 5, 1933. R. RUDENBERG THERMIONIG TUBE Filed April 12 I 'll A'TTORNEY Patented Dec. 5,"1933 r v UNITED 'STATES PATENT OFFICE ssuers THERMIONIC TUBE Reinhold Riidenberg, Berlin-Grunewald, Germany, assignor to Westinghouse Electric &

Manufacturing Company, a corporation of Pennsylvania Application April 12, 1926, Serial No. 101,268, and in Germany June 15, 1925 4 Claims. (01. 250-275 My invention relates to vacuum tubes and Fig. 6 is a diagram illustrating the distribution particularly to high-power tubes such as are used of potentials in the structure shown in Fig. and in radio broadcasting stations. Fig. 7 is a longitudinal section through a water- It is an object of my invention to protect the cooled tube embodying my invention. 5 cathodes of vacuum tubes from mechanical As illustrated in Fig. 1, a vacuum tube is usu- 55 stresses resulting from electrostatic forces. ally provided with a cylindrical anode 1, and a It is a further object of my invention to provide cathode 2, having the form of two parallel heated vacuum tubes having a supplementary electrode sections of filament. The electro-static field bewhich shall produce a field tending to neutralize tween the anode and the two-part cathode will 10 the field of the anode at the cathode, not be symmetrical about the axis of the tube 60 It is a further object of my invention to provide because of the double character of the filament. a symmetrical arrangement of the anode, cathode n a tube of this construction, there will be forces and supplementary electrode. acting upon the filament sections. When the It is a further object or this invention to provoltage is h h, these foreesresult i sufiicient vide concentric electrodes having such respective stress to materially lessen the life of the fila- 65 radii that the cathode shall be located where ent. r the mechanical stressesupon it will be a mini- S t at d in a S pp e de mum. comprised of two portions 3 and 4 is provided. The cathode, in one form of my invention, is This electrode is maintained at such potential preferably an assembly of filaments forming a that its field tends to neutralize the mechanical 7 cylindrical surface. When the electrodes are areffect o e fi 0f th anode p n t filament rangedin this way, it is desirable that the radius 3 u trat s another form of the device in of the cathode-assembly shall be the geometric which 1 Single b y 5,1heihteihed at the potential. mean between the radii of the anode and of the j described, neutralizes the mechanical supplemental electrode. a traction of the anode 1 upon the cathode- 7 It isa further object of this inventionto provide seebions a supplemental electrode in the form of an exten- Fig; 4 illustrates the form ic e b y sion of the anode, whereby the two electrodes are Corresponding t0 the y will e w e maintained at the same potential. r the cathode2l is infour parts instead of two.

It is a further object of my invention to so arthe Cathode 22 of y Parts so range the parts of a vacuum tube that the anode a a d in cylindrical m. The supp m n al and the supplemental electrode shall constitute electrode 52 thenbecemes a Cylindrical tube, and the major portion of the evacuated envelo e, the a h d comprises a p u ity of parall l xwhereby avery effective cooling surface is protehdinEwiIeS, connected in Zig-Zag form, a idei properly supported. The inner member is 35 ot objects f invention will become charged to a suitable potential to counteract the apparent from the following detailed description electrostatic forces. Ihe electrostatic forces on and the accompanying'dmwmg in which the cathode wires W111 ust balance when the Fig 1 is a diagram illustrating the usual ab radius of the cathode has apredetermined length,

40 in accordance with the. value of the voltage E1 of gi g f illustrating one the outer anode, the voltage E2 of the inner f m v d member and the radii of the cylinders n and r2 0 o f F v (see Fig. 6). A condition is that the electrostatic 3 1S a $111111 dlagram lllustretme another field strengths at the limits of the outer and the 45 form inner cathode space are equal and opposite.

Fig. 4 is a similar diagram illustrating still another form; r

Fig. 5 is a similar diagram illustrating the form of the device when the cathode filaments are c 50 very numerous; r a

Fora cylindrical co-axial arrangement, the field strength for each radius r is given by in which C is a constant. The potential of each point is determined by E C log t (2) For complete freedom from stresses of all cathode wires at the radius To, the constants must meet the condition The voltages of the anode cylinders 1 and 52 relative to the cathode 22 areaccording to Equation 2 as follows,

E C log and if the Equation 4 is employed '2 E2: C2 log there is obtained for freedom from stresses the following:

If the cathode radius m is assumed fixed relative to the anode radii T1 and r2, there is secured a predetermined ratio of the voltages of the two anodes, namely But if the voltage ratio is assumed as fixed, a predetermined radius of cathode that is necessary is obtained by simple transformation of Equation 6, as follows:

'0 2 E1 a ts is It is best to make the voltages of the two anodes the same, so that they can be connected in parallel to each other inside the tube, and in this case the cathode radius is given by Equation 8 as follows 7 that is, it is equal to the geometric mean of the two anode. radii.

When the incandescent cathode and the inner member are in the form of two concentric cylinders, we have the further advantage that-the tube can be easily cooled, as by surrounding the outer side of the outer anode and the inner side of the hollow inner member with a cooling fluid and Fig. 7 shows such an electron tube. The inner cylinder 52, located concentrically with the outer anode 1, is of pot shape, and as the inner cylinder and the outer anode are energized at the same voltage, they may merge into each other at their lower edges.

The tube is provided with, a cover 6, which is traversed by a cooling, fluid. Close to the interior of the cylinder 52, there is provided a tube 7 and at the top of the cover 6 is an additional tube 8 for the circulation of the cooling fluid. The outer anode 1 is fused into a glass member 9, in well .known manner, and which member is provided on an inner portion with the means for supporting the cathode wires.

To use the invention in control tubes, it is only necessary to build into the tube a control grid on both sides of the cylindrical cathode, and if the distribution of the potential in the tube is changed, it is easy to determine the best radius of the wires for freedom from stresses.

The incandescent wire may be located in any desired manner at the surface of the cylinder having the radius 7'0, either along the surface longitudinally thereof, or spirally around the cylinder. The individual portions of the wire may be connected in series or in parallel, in order to avoid excessive voltage differences along the wire and the resulting unequal effects on the electron emission.

If the theoretical position of the wires is not maintained, there will be certain forces exerted thereon, and it is preferable to mount the wires resiliently, so that they are under a moderate longitudinal tension and can follow lateral forces by yielding movements.

While the various electrodes are of circular form, in the drawings, they may have any other form, such as polygonal, elliptical, or still more complicated forms.

It will be obvious to those skilled in the art that many other forms of my invention exist and the only limitations thereon are those necessitated by the prior art or imposed by the following claims. p

I claim as my invention:

1. A vacuum-tube device comprising a cathode in circular symmetry about the axis of the tube, a cylindrical anode coaxial therewith, a cylindrical electrode also coaxial therewith said cathode'being between said anode and said electrode the radius of the cathode being approximately the geometrical means of the radii of the anode and the electrode.

,2. A vacuum tube-comprising a cathode, an evacuated envelope, and a water jacket surrounding said anode, said envelope comprising a metallic portion including an exterior anode and a reentrant member of thimble shape electrically continuous therewith, the cathode being between said anode and said reentrant member.

.3. A vacuum tube comprising a cathode, an evacuated envelope, said envelope comprising an anode having a metallic reentrant portion, a water jacket surrounding said anode, and a water pipe extending into said reentrant portion and cooperating with said water jacket to'provide circulation of water over all the surface of said anode, the cathode being between a portion of said anode and said reentrant portion.

4. A vacuum-tube device having three concentric electrodes each of circular cross section, the middle electrode beingmechanically weaker than either of the other electrodes wherein the radii of the respective electrodes are proportioned to fit in the formula 1 B EJE' 12 E2 log; 

